Driving Rain Tests

The test specimen of 2 m width by 3 m length (till the ridge) will be roofed with the tiles or roofing stones supplied by the manufacturer. The test specimen is installed such that the vertical axis of the roof is inclined against the vertical axis of the wind tunnel to test several roof pitch angles.

The rain simulation is obtained by spraying water into the air stream above the test specimen using 2 rows of nozzles. From fundamental studies it is obvious that rain penetration is caused mainly by the wind induced pressures at the head laps pushing the surface water flowing downs the roof excerpt into the batten space. Therefore the water spray is adjusted in such a way as to simulate the rainfall on roof of 10 m length. The test results may therefore be applied to pitched roof of typical apartment blocks, office buildings, as well for small family dwellings.

The test specimen is provided with carefully sealed PE-underlays over the rafters. Any water penetrating into the batten space drips onto and drains down the underlay. It will flow into a gutter fixed at the lower side of the underlay, collected in a vessel and measured. With these information the DRI (Driving Rain Index) may be determined.